.tab-x {
    display: flex;
    flex-direction: row-reverse;
    justify-content: flex-end;
    padding-left: 20px;
    border-bottom: 1px solid rgba(0,0,0,.1);
}
.tab-a {
    --backgroundColor: #fff;
    background-color: var(--backgroundColor);
    line-height: 20px;
    padding: 10px 20px;
    border-radius: 16px 16px 0 0;
    filter: drop-shadow(0 -1px 1px rgba(0,0,0,.1));
    position: relative;
}
/* 创建外侧圆弧 */
.tab-a::before,
.tab-a::after {
    content: '';
    position: absolute;
    bottom: 0;
    width: 16px; height: 16px;
}
.tab-a::before {
    background: radial-gradient(circle at 0 0, transparent, transparent 16px, var(--backgroundColor) 17px);
    right: 100%;
}
.tab-a::after {
    background: radial-gradient(circle at 100% 0, transparent, transparent 16px, var(--backgroundColor) 17px);
    left: 100%;
}
.tab-a.active {
    --backgroundColor: teal;
    color: #fff;
    z-index: 1;
}